#### A decimal to binary converter (utilizing "two's complement)
#### Made by Anthony Sinnott
#### Version 2.1 - Supports negitive numbers, has cleaner code, and is fully commented 

# define method to convert possitive value
def posbincon(value):
	# detect if the value equals zero or not
	if value == 0:
		binary = str(value)
		return binary
	else:
		binary=[]
		# evaluate each digit to determine if it is true or false
		while(value > 0): 
			if value&1:
				binary.append("1")
			else:
				binary.append("0")
			# go on to next didgit (right-bitshift)
			value = value>>1
		# convert list to string and reverse it
		binary = "".join(binary)[::-1]
		return binary
		
# define method to convert negitive value
def negbincon(value):
	# binary is the possitive output
	binary = posbincon(value)
	# lenbin is the length of the possitive output
	lenbin = len(binary)
	# conbin is the mechinism used to stop lines 30-32
	conbin = 0
	while conbin == 0:
		# if possitive output's current holding number is one, conbin is activated
		if binary[lenbin-1] ==  "1":
			conbin = 1
		# this is to determine one numbers should and shouldn't be rotated
		lenbin = lenbin - 1
	# notuse contains any numbers that won't be rotated, binary is the opposite
	notuse = binary[lenbin:]
	binary = binary[:lenbin]
	# binary2 will contain the new (rotated) set of numbers
	binary2 = ""
	# each digit is evaluated, 0s converted to 1s, 1s to 0s
	while(binary != ""):
		if binary[0] == "0":
			binary2 = binary2 + "1"
		if binary[0] == "1":
			binary2 = binary2 + "0"
		binary = binary[1:]
	# appends the numbers not rotated to the ones that were
	binary = binary2 + notuse
	return binary

# small introduction
print "Welcome to the Ultimate, low budget binary to decimal converter"
# the two's complement is a method of representing both negitive and possitive numbers in binary format
print "Now including Two's Complement"
print ""

# quit is the mechanism used to stop the program
quit = 0
while quit == 0:
	
	# allows the user to enter the value to be converted
	value = input("Enter the number here:> ")
	# saves the value in string format
	decimal = str(value)

	# gives appropriate output depending on weither the value is possitive or negitive
	if value >= 0:
		print "The binary value of " + decimal + " is " + posbincon(value)
	else:
		value = -value
		print "The binary value of " + decimal + " is " + negbincon(value)  
	print ""
	# asks the user if they want to continue to use the program
	quit = input("Quit, yes or no? 1 or 0:> ")
	print ""
                                       
#### Program produce by Anthony Sinnott using a template made by Spencer
####
#### How the "two's complement" conversion works:
#### Numbers are reversed
#### 1 is added to the right-most digit
####
#### Shortcut used in this program:
#### Values including and beyond the rightmost 1 are held
#### All other values are reversed
####
#### For more information visit:
#### http://en.wikipedia.org/wiki/Two's_complement
####
#### Thank you for supporting this program :)